Field of the Invention
The invention relates to a field-effect controlled semiconductor component and to a method for manufacturing such a semiconductor component.
Such a component is for example a vertically configured field-effect transistor which is described, for example, by Stengl, Tihanyi in the book xe2x80x9cLeistungs-MOSFET-Praxisxe2x80x9d (Power MOSFET in practice), Pflaum Publishers, Munich, 1992, page 37. The field-effect transistor has a drain zone, as first connection zone, with which a contact can be provided on a rear side of the semiconductor body, and a second connection zone, as a source zone, with which a contact can be provided on a front side opposite the rear side. The source zone is formed in what is referred to as a body zone which is in turn formed in a drift zone above the drain zone. The drain zone, the source zone and the drift zone are of the same conductivity type, while the body zone is of a complementary conductivity type. The drift zone is weakly doped when compared to the drain zone and the source zone and, when a voltage is applied between the drain and source, it absorbs a large part of this voltage. Above the body zone, a control electrode is formed as a gate electrode which, when a suitable drive potential is applied, brings about a conductive channel in the body zone between the source zone and the drift zone. The gate electrode forms, with the region of the semiconductor body lying below it, a capacitor which has to be charged to switch through the transistor and discharged to switch off the transistor, and which thus influences the switching behavior of the transistor.
Such components are suitable, depending on their specific embodiments, for switching currents up to several tens of amperes with a dielectric strength of up to several hundred volts.
It is accordingly an object of the invention to provide a semiconductor component which overcomes the above-mentioned disadvantages of the heretofore-known semiconductor components of this general type and which in particular for applications in which voltages of less than 100 volts are to be switched or blocked, provides a low value for the gate capacitance.
With the foregoing and other objects in view there is provided, in accordance with the invention, a semiconductor component, including:
a semiconductor body having a first side and a second side opposite the first side, the semiconductor body defining a vertical direction and a lateral direction transverse to the vertical direction, the vertical direction extending from the first side to the second side;
the semiconductor body including a first connection zone of a first conductivity type for providing a contact at the first side of the semiconductor body;
the semiconductor body including a second connection zone of the first conductivity type for providing a contact at the second side of the semiconductor body;
the semiconductor body including a drift zone adjoining the first connection zone and extending in the vertical direction as far as the second side of the semiconductor body;
the semiconductor body including a body zone of a second conductivity type disposed between the second connection zone and the first connection zone or the drift zone; and
a control electrode insulated from the semiconductor body, the control electrode being disposed above the body zone such that the control electrode substantially does not overlap with the drift zone and the second connection zone in the lateral direction.
According to another feature of the invention, the drift zone and the body zone have respective regions adjoining one another; and the respective regions are doped such that, when a reverse voltage is applied between the first connection zone and the second connection zone, at least the drift zone is completely emptied of charge carriers.
According to another feature of the invention, the body zone has a first zone with a first doping concentration of the second conductivity type and a second zone with a second doping concentration of the second conductivity type, the first doping concentration is higher than the second doping concentration; and the first zone adjoins the second connection zone and the second zone.
According to yet another feature of the invention, the body zone has a given zone of the second conductivity type, the given zone is disposed underneath the control electrode and at a given distance from the second side, the given zone of the second conductivity type is more heavily doped than a remainder of the body zone.
According to another feature of the invention, the drift zone has at least two adjacent zones, a first one of the at least two adjacent zones is of the first conductivity type and a second one of the at least two adjacent zones is of the second conductivity type; and the at least two adjacent zones extend from the first connection zone in the vertical direction of the semiconductor body toward the second side of the semiconductor body.
According to a further feature of the invention, the drift zone has a plurality of respectively alternating zones of the first and second conductivity types; and the plurality of respectively alternating zones extend from the first connection zone in the vertical direction of the semiconductor body toward the second side of the semiconductor body.
According to another feature of the invention, the at least two adjacent zones of the drift zone extend as elongated zones in the lateral direction of the semiconductor body.
According to another feature of the invention, the body zone, the second connection zone and the control electrode extend as elongated zones in a further lateral direction of the semiconductor body transverse to the lateral direction.
According to yet another feature of the invention, the drift zone has a given zone of the first conductivity type, the given zone is more heavily doped than a remainder of the drift zone, the given zone adjoins the body zone and is disposed at the second side of the semiconductor body.
The component according to the invention has a first connection zone of a first conductivity type, with which contact can be made on a first side of a semiconductor body, a second connection zone of the first conductivity type, with which contact can be made on a second side of the semiconductor body lying opposite the first side, a drift zone which adjoins the first connection zone and extends in the vertical direction of the semiconductor body as far as the second side of the semiconductor body, a body zone of a second conductivity type which is formed between the second connection zone and the drift zone, and a control electrode which is formed over the body zone and which is insulated from the semiconductor body. According to the invention, the control electrode is formed at least approximately without overlap with the drift zone and the second connection zone in the lateral direction of the semiconductor body. This results in a capacitance between the control electrode and the drift zone which is less than that of similar conventional components, that is to say a smaller gate/drain capacitance or Miller capacitance, as a result of which faster switching operations of the semiconductor component are possible.
Ideally, such semiconductor components have a small value for the product of the gate/drain capacitance and switch-on resistance, the switch-on resistance being the effective electrical resistance between the first and second connection zones when the control electrode is driven to the conductive state.
According to one embodiment of the invention, there is therefore provision that the regions of the body zone and of the drift zone which adjoin one another are doped in such a way that, when a voltage is applied between the first and second connection zones and the control electrode is not drivenxe2x80x94that is to say when there is no conductive channel present in the body zonexe2x80x94at least the drift zone is completely emptied, i.e. completely drained of charge carriers. xe2x80x9cCompletely emptiedxe2x80x9d means that there are only the ionized non-moving impurity atoms present in the drift zone and no longer any freely moving charge carriers. The charge carriers of the drift zone are compensated by charge carriers of the body zone, resulting in a comparatively high breakdown voltage of the semiconductor component. On the other hand, as a result of the compensation of the charge carriers in the drift zone which occurs, the drift zone can be more heavily doped than in components without charge carrier compensation, resulting in a low switch-on resistance of the semiconductor component when there is a high breakdown voltage. The body zone preferably has a more heavily doped region around the first connection zone and a more weakly doped region adjacent to the drift zone, such that it is possible for the more weakly doped region to be emptied by the drift zone.
According to a further embodiment, in the body zone, a more heavily doped region is provided underneath the body zone, a more weakly doped region being present between the surface of the semiconductor body and this more heavily doped region in order to form a channel. The more heavily doped region prevents a space charge zone (depletion zone), which is produced when a voltage is applied between the first and second connection zones, from extending as far as the channel region underneath the control electrode in the body zone.
The product of the control electrode capacitance and switch-on resistance is smaller with the component according to this embodiment than with such components according to the prior art.
In a further embodiment of the invention, the drift zone has a number of alternating zones of the first and second conductivity types, which zones extend in each case in the vertical direction of the semiconductor body toward the second side of the semiconductor body starting from the first connection zone. These respectively alternating zones with different conductivity types are doped here in such a way that, when a voltage is applied between the first and second connection zones and the drive electrode is not driven, they empty one another, or that at least the zones of one conductivity type are completely emptied.
These differently doped zones of the drift zone additionally extend in elongated fashion in a first lateral direction of the semiconductor body, the body zone which is formed in the drift zone, the second connection zone and the associated control electrode extending in elongated fashion in a second lateral direction of the semiconductor body transversely with respect to the first lateral direction.
In this embodiment of the invention, the switch-on resistance, which is mainly dependent on the doping of the alternating zones in the drift zone, can be set independently of the resistance of the channel in the body zone, which resistance is dependent not only on the doping of the body zone but also on the channel length.
The drift zone preferably has, adjacent to the body zone, a heavily doped, also elongated zone of the first conductivity type in order to xe2x80x9ccollectxe2x80x9d charge carriers of the first conductivity type which leave the channel zone, and to pass the charge carriers on to the first connection zone of the first conductivity type via the zones of the first conductivity type in the drift zone.
With the objects of the invention in view there is also provided, a method for manufacturing a semiconductor component, the method includes the steps of:
providing a semiconductor substrate of a first conductivity type in order to provide a first connection zone;
forming a layer of a second conductivity type on the semiconductor substrate;
manufacturing at least one plate-shaped control electrode on the layer of the second conductivity type such that the at least one plate-shaped control electrode is insulated from the layer of the second conductivity type;
manufacturing a drift zone of the first conductivity type such that, at least in a region of a surface of the layer of the second conductivity type, the drift zone is directly or indirectly self-aligned with respect to a first edge of the at least one plate-shaped control electrode and such that the drift zone extends in a vertical direction of a semiconductor body as far as the semiconductor substrate; and
manufacturing a second connection zone of the first conductivity type in the layer of the second conductivity type such that, at least in a region of a surface of the layer of the second conductivity type, the second connection zone is self-aligned with respect to a second edge of the at least one plate-shaped control electrode disposed opposite the first edge.
Another mode of the method according to the invention includes manufacturing a spacer at a side of the first edge of the at least one plate-shaped control electrode for manufacturing the drift zone; and manufacturing the drift zone self-aligning with respect to the spacer in a region of the layer of the second conductivity type, the region adjoining a surface of the layer.
A further mode of the method according to the invention includes, prior to manufacturing the second connection zone, producing a doped zone of the second conductivity type in the layer of the second conductivity type, such that the doped zone is more heavily doped than a remainder of the layer of the second conductivity type.
Another mode of the method according to the invention includes producing the doped zone by diffusing doping atoms of the second conductivity type into the layer of the second conductivity type.
Yet another mode of the method according to the invention includes manufacturing the drift zone by implanting doping atoms of the first conductivity type into the layer of the second conductivity type.
Another mode of the method according to the invention includes manufacturing the second connection zone by implanting doping atoms of the first conductivity type into the doped zone of the layer of the second conductivity type.
With the objects of the invention in view there is also provided, a method for manufacturing a semiconductor component, the method includes the steps of:
providing a semiconductor substrate of a first conductivity type in order to provide a first connection zone;
applying a layer onto the semiconductor substrate such that the layer has a given conductivity type selected from the group consisting of the first conductivity type and a second conductivity type;
manufacturing compensation zones in the layer such that the compensation zones have a conductivity type complementary to the given conductivity type of the layer and such that the compensation zones extend as far as the semiconductor substrate;
manufacturing at least one control electrode on the layer such that the at least one control electrode is insulated from the layer;
manufacturing a body zone of the second conductivity type in the layer underneath the at least one control electrode;
manufacturing a second connection zone of the first conductivity type in the body zone such that the second connection zone is directly or indirectly self-aligned with respect to a first edge of the at least one control electrode, at least in a region of a surface of the layer; and
manufacturing a self-aligned zone of the first conductivity type in the layer such that the self-aligned zone is self aligned with respect to a second edge opposite the first edge of the at least one control electrode, at least in a region of a surface of the layer.
Another mode of the method according to the invention includes manufacturing the body zone by using a diffusion method.
Another mode of the method according to the invention includes manufacturing the second connection zone by using an ion implantation process.
A further mode of the method according to the invention includes manufacturing the self-aligned zone by using an ion implantation process.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a semiconductor component which can be controlled through the use of a field-effect and a method for manufacturing such a semiconductor component, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.